Broad band balun transformer



Feb. 16, 1960 H. JASIK BROAD BAND BALUN TRANSFORMER Filed June 26, 1957e)T-Q IN V EN TOR.

BY pr/Ja %%z;

Unie dttes Patnt nRoAn BAND BALUN TRANSFORMER Henry Jasik, Flushing,N.Y., assignor, by mesne assignments, to the United States of America asrepresented by the Secretary of the Navy Application June 26, 1957,Serial No. 668,274

1 Claim. (Cl. 333-26) This invention relates to a transformer device ina particular circuit using high frequencies.

The object of this invention relates to a system of impedance matchingin a particular circuit for maximum power transfer.

A further object of this invention is a particular design of a balun andtransformer which occupies a much reduced space than formerly occupied.

A still further object of this invention is a system of feeding a highimpedance line from a low impedance line over a wide frequency rangewithout introducing an appreciable standing wave ratio (SWR).

These and other objects will be readily apparent to those skilled in theart from an examination of the following description and enclosed sheetof drawings wherein,

Figure 1 illustrates the basic balun and transformer,

Figure 2 illustrates the balun and transformer as in Figure 1 but withthe input and output on the same side,

Figure 3 illustrates the transformer system together with a shieldingbox, and

Figure 4 illustrates the transformer system wherein the balun conductorsare coiled for high impedance.

Referring to Figure 1, the balun consists of an unbalanced coaxial inputcomprising an outer conductor 1 and a concentric inner conductor 2;paralleling the conductors is a balanced line comprising a conductor 3shunted to the outer conductor 1 by a shunt 4.

On the opposite side of the balun, a coaxial conductor having an outerconductor 5 and a concentric inner conductor 6 is paralleled by asimilar coaxial line having an outer conductor '7 and an inner conductor8. The two outer conductors are joined together by a connector 15. Theinner conductors 6 and 8 are connected to a load 14. The right handportion of the circuit forms a high impedance balanced load; the balunstructure in the system is of low impedance with the high to lowimpedance ratio being of the order of 4 to 1.

The cross connections are as follows: a lead 13 from the inner conductor2 is joined to conductor 3; lead 12 joins the outer conductors 1, 5;lead 9 connects conductors 3, 7; lead 11 connects conductors 1, 8; andlead connects conductors 3 and 6.

By means of the cross connection shown, the high impedance is reduced toa low impedance and, in the instant values used, from 200 ohms to 50ohms in an ideal 4 to 1 ratio.

Figure 2 shows the same basic structure as Figure 1 except that theoutput and input originate from the same side. inthis modificationhowever, leads 9 and 12 are eliminated and the conductors abut eachother. Thus outer conductors 105 and 101 abut and parallel each other toeliminate lead 12 while conductors 103 and 107 abut and parallel eachother to eliminate lead 9.

The impedance values and ratios of Figure 2 are identical with those ofFigure 1.

Figure 3 shows a structure similar to Figure 2. Conductors 201 and 205abut and are parallel to each other; conductors 203 and 207 also abutand are parallel to each other. Cross-connections 210,211 and 213 areidentical with 10, 11 and 1.3 of Figure 1 and 110, 111 and 113 of Figure2.

In this modification, however, the structure centering around thetransformer cross-connections is encased in a shielding box 216.

The shunt reactance across the coaxial input is a function of the outerconductor diameters and the size of the shielding box. In order torealize a large impedance band width such that the SWR is kept as closeto unity as possible, this shunting reactance is made high. Toaccomplish this, the characteristic impedance of the transmission lineformed by the shield and the balun conductors is made correspondinglyhigh.

Figure 4 shows a modified form of the balun in which the balunconductors have been coiled into an inductance. The circuit connectionsof this figure correspond to those in Figure 3. This type of structurehas been used for high impedance delay lines as it can realizeimpedances of the order of 500-1000 ohms, as compared to maximumcharacteristic impedances in Figure 3 of -150 ohms.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claim the invention maybe practiced otherwise than as specifically described.

What is claimed is:

A high impedance delay line circuit wherein a high impedance balancedtransmission line is fed from a low impedance unbalanced line andcircuit comprising a pair of high impedance coaxial lines coupled tothebalanced line; a low impedance coaxial line coupled to the unbalancedline; a low impedance conductor substantially equal in length to the lowimpedance coaxial line, the low impedance conductor being disposedadjacent and conductively connected to the outer conductor of one highimpedance coaxial line, the outer conductor of the low impedance coaxialline being disposed adjacent and conductively connected to the outerconductor of the other high impedance coaxialline; means connecting theouter conductor of the low impedance coaxial line to the inner conductorof the said one high impedance coaxial line; means connecting the innerconductor of the low impedance coaxial line to the low impedanceconductor; and means connecting the inner conductor of the said otherhigh impedance coaxial line to the low impedance conductor, the said onehigh impedance coaxial line being coiled with the low impedanceconductor and the said other high impedance coaxial line being coiledwith the low impedance coaxial line to increase the inductive impedanceof the circuit.

References Qited in the file of this patent UNITED STATES PATENTSFOREIGN PATENTS Germany Sept. 17, 1953

